This invention relates to a process for the polymerization of caprolactam or amino caproic acid. More specifically, this invention relates to a method to control thermal degradation and viscosity increase while removing extractables in a polymer finisher under vacuum.
The prior art patents, of which we are aware, considered to be most pertinent to this invention are U.S. 2,904,109 to Malm, U.S. 2,731,081 to Mayner, U.S. 3,578,640 to Twilley, Coli, Jr., and Roth J. and U.S. 3,526,484 to Kilpatrick. The pertinent portions of all the above patents are hereby incorporated by reference. The Malm and Mayner patents teach removing monomers from a polycaproamide melt by sweeping with steam prior to spinning. Kilpatrick and Twilley et al. teach direct spinning of nascent polymer but the monomer and other water extractables are removed by vacuum venting. These latter patents teach use of a polymer finisher (labeled 60 in the Twilley figure and labeled 8 in the Kilpatrick figures) but do not teach maintaining high partial pressure of steam in the finisher. Nor do these references teach control of polymer viscosity, or even recognize a polymer degradation problem in the finisher.